Reading a file and sorting by columns

[lawgarra318]

To read a file with the format:

Susan 24 23 60.4
Sam 32 19 93.5
James 16 92 48

and sort it by an arbitrary column, for example, by column 0, the output should be:

James 16 92 48
Sam 32 19 93.5
Susan 24 23 60.4

Could any one take a look at the following codes, which are supposed to work...
Any help would be appreciated

  #include<iostream>	// Provides cout, etc.
#include<fstream>	// Provides open(), etc.
#include<cstring>	// Provides strcpy(), etc.
#include<cctype>	// Provides toupper()
using namespace std;

const int MAXNAMESIZE = 10;		// Allows for 26 characters in name and null character '\o'
const int MAXCLASSSIZE = 50;	// Maximum of 50 students in class
const char QUIT = 'Q';

struct student
{
	char name[MAXNAMESIZE];	// Name of student
	double score;			// Grade point average of student
};


void read_array_of_struct(istream& is, student s[], int& n, int capacity);
// Postcondition: n records have been read into s[] from input stream, and n<=capacity.

void write_array_of_struct(ostream& os, const student s[], int n);
// Precondition: s[] has n valid records
// Postcondition: The field values of these records are written to output stream os

void print_menu();
// Postcondition: The menu of options is printed to the screen

char get_choice();
// Postcondition: The users choice is returned

void sort_on_name(student s[], int n);
// Precondition: s[] has n valid records
// Postcondition: These records are sorted alphabetically

void sort_on_score(student s[], int n);
// Precondition: s[] has n valid records
// Postcondition: These records are sorted numerically by GPA

double get_av(const student s[], int n);
// Precondition: s[] has n valid values
// Postcondition: The average GPA is returned

void write_av(ostream& os, double average);
// Precondition: gpa_av has a valid value
// Postcondition: gpa_av is written to output stream os

int main()
{
	student s[MAXCLASSSIZE];	// Creates array elements s[0], s[1], s[MAXCLASSSIZE-1] of type student

	int n;			// Number of records read
	char choice;	// Menu choice from user
	double score_av;	// Average GPA of all students

	ofstream fout;	// Internal name for output file
	ifstream fin;	// Internal name for input file

	fout.open("output.txt");
	fin.open("tea.txt");

	decimal_format(cout);
	decimal_format(fout);

	read_array_of_struct(fin,s,n,MAXCLASSSIZE);

	// Print menu to the screen
	print_menu();

	// Get user choice for menu
	choice = get_choice();

	// Process until QUIT is entered
	while(toupper(choice) != QUIT)
	{
		switch(toupper(choice))
		{
		case '0': print_menu();	// Prints menu to screen
				  break;

		case '1': sort_on_name(s,n);	// Sorts array alphabetically
				  cout << "\nSorted by name:\n\n";
				  write_array_of_struct(cout,s,n);	// Write sorted array to screen
				  fout << "\nSorted by name:\n\n";
				  write_array_of_struct(fout,s,n);	// Write sorted array to output file
				  break;

		case '2': sort_on_score(s,n);	// Sorts array numerically by student number
				  cout << "\nSorted by GPA:\n\n";
				  write_array_of_struct(cout,s,n);	// Write sorted array to screen
				  fout << "\nSorted by GPA:\n\n";
				  write_array_of_struct(fout,s,n);	// Write sorted array to output file
				  break;

		case '3': score_av = get_av(s,n);		// Gets average of all GPA's
				  write_av(cout,score_av);	// Writes average of all GPA's to screen
				  write_av(fout,score_av);	// Writes average of all GPA's to output file
				  break;

		default:  // Inform user of invalid choice
				  cout << "\nSorry, " << choice << " is not a valid option";
				  cout << "\nPlease try again.\n";
		}

	// Get next choice from user
	choice = get_choice();

	}

	// Close output and input files
	fout.close();
	fin.close();

	return 0;
}


void decimal_format(ostream& os)
{
	os.setf(ios::fixed);
	os.setf(ios::showpoint);
	os.precision(2);
}

void read_array_of_struct(istream& is, student s[], int& n, int capacity)
{
	char temp[MAXNAMESIZE];		// Temporary storage for student name

	n = 0;	// Initiliazes n to a value of 0, as no records have been read

	is.get(temp,MAXNAMESIZE);
	while((!is.eof()) && (n < MAXNAMESIZE))
	{
		strcpy(s[n].name,temp);	// Copy temp into s[n].name
		is >> s[n].score;				// Read student GPA


		n++;		// Add 1 to student count

		is.get(temp,MAXNAMESIZE);	// Read next name, if there is one
	}

}

void write_array_of_struct(ostream& os, const student s[], int n)
{
	for(int i=0; i<n; i++)
	{
		os << s[i].name;			// Prints student name
		os.width(10);				// Right justify by width of 10
		os << s[i].score << endl;		// Prints GPA
	}
}

void print_menu()
{
	cout << "\n0 - See menu again"
		 << "\n1 - Sort by name"
		 << "\n2 - Sort by student number"
		 << "\n3 - Sort by GPA"
		 << "\n4 - Find average GPA"
		 << "\n" << QUIT << " - Quit this program\n\n";
}

char get_choice()
{
	char c;		// Local variable to store user choice

	// Get choice from user
	cout << "\nPlease enter a choice (0 to see menu):";
	cin >> c;

	return c;
}

void sort_on_name(student s[], int n)
{
	student temp;	// Local variable used to swap records

	for(int i=0; i<n; i++)
	{
		for(int i=0; i<n; i++)
		{
			// If s[i].name is later in alphabet than s[i+1].name, swap the two records
			if(strcmp(s[i].name,s[i+1].name) > 0)
			{
				temp = s[i];
				s[i] = s[i+1];
				s[i+1] = temp;
			}
		}
	}
}


void sort_on_score(student s[], int n)
{
	student temp;	// Local variable used to swap records

	for(int i=0; i<n; i++)
	{
		for(int i=0; i<n; i++)
		{
			// If s[i].gpa is greater than s[i+1].gpa, swap the records
			if(s[i].score > s[i+1].score)
			{
				temp = s[i];
				s[i] = s[i+1];
				s[i+1] = temp;
			}
		}
	}
}

double get_av(const student s[], int n)
{
	double av,			// Local variable used to store average
		   sum = 0;		// Sum of all GPA's

	// Return value of 0 if no data is found
	if(n == 0)
	{
		return 0;
	}

	for(int i=0; i<n; i++)
	{
		// Add GPA to sum of GPA's
		sum = sum + s[i].score;
	}

	// Calculate the average GPA
	av = sum / n;

	return av;
}

void write_av(ostream& os, double average)
{
	os << "The average GPA is " << average << endl << endl;
}